1. Field of the Invention
The present invention relates to a process for preparing tribromoneopentyl chloroalkyl phosphates. The tribromoneopentyl chloroalkyl phosphates can give flame retardancy and very low fogging property to polyurethane foam.
2. Description of Related Art
Polyurethane resin as a typical thermosetting resin is widely used in manufacture of various kinds of daily products including automobile parts because it can be obtained at a relatively low price and has remarkable characteristics such as good moldability. However, as polyurethane foam is combustible and tends to cause uncontrollable combustion once it catches fire, a lot of efforts have been made in this industry for flame-retarding of polyurethane foam. Today in some fields using polyurethane foam such as automobile interior furnishing, the flame-retardancy is legally required. Also, as environmental preservation is socially highlighted and dioxin (halodibenzodioxins) and CFC (chlorofluoro carbon) problems are zealously discussed, low fogging property in addition to the flame retardancy is a critical issue in auto-parts manufacture using polyurethane foam.
In order to give flame-retardancy to polyurethane foam, tribromoneopentyl chloroalkyl phosphates are conventionally added, which are disclosed in for example U.S. Pat. No. 4,046,719, U.S. Pat. No. 4,083,825 and Japanese Examined Patent Publication No. Sho61(1986)-3797. However, it has been found that the tribromoneopentyl chloroalkyl phosphate products as disclosed therein contain, in addition to the end flame-retardant tribromoneopentyl bis(chloroalkyl)phosphates, about 10 wt % tris(chloroalkyl)phosphate which is a monomeric component, about 20 wt % bis(tribromoneopentyl) chloroalkyl phosphate and about 5 wt % tris(tribromoneopentyl) phosphate which are crystalline components.
When a tribromoneopentyl chloroalkyl phosphate product is used as flame-retardant, it is desirable that the content of the monomeric component is as low as possible since it easily vaporizes by heat and thus adversely affects the fogging property.
It is also desirable that the content of the crystalline bis(tribromoneopentyl)chloroalkyl phosphate and tris(tribromoneopentyl)phosphate is as low as possible because they affect the viscosity of product, producing bad effects on the workability due to high viscosity and solidification.
Under these circumstances, there has been demand for a tribromoneopentyl chloroalkyl phosphate product exhibiting low fogging property with the lowest content of monomers and providing a low viscosity for good workability with the lowest content of crystalline components.